This disclosure relates to a sensor arrangement for an Integrated Pressure Management Apparatus (IPMA) that manages pressure and detects leaks in a fuel system. This disclosure also relates to a sensor arrangement for an integrated pressure management system that performs a leak diagnostic for the headspace in a fuel tank, a canister that collects volatile fuel vapors from the headspace, a purge valve, and all associated hoses. And this disclosure also relates to controlled duty cycle purging that provides active leak detection recognition by the IPMA while the engine is operating and able to accept evaporative purging.
In a conventional pressure management system for a vehicle, fuel vapor that escapes from a fuel tank is stored in a canister. If there is a leak in the fuel tank, canister or any other component of the vapor handling system, some fuel vapor could exit through the leak to escape into the atmosphere instead of being stored in the canister. Thus, it is desirable to detect leaks as a result of a 0.5 millimeter or greater break in the vapor handling system.
In such conventional pressure management systems, excess fuel vapor accumulates immediately after engine shutdown, thereby creating a positive pressure in the fuel vapor management system. Thus, it is desirable to vent, or xe2x80x9cblow-off,xe2x80x9d through the canister, this excess fuel vapor and to facilitate vacuum generation in the fuel vapor management system. Similarly, it is desirable to relieve positive pressure during tank refueling by allowing air to exit the tank at high flow rates. This is commonly referred to as onboard refueling vapor recovery (ORVR).
The present invention provides a sensor arrangement for an integrated pressure management apparatus. The sensor arrangement comprises a chamber having an interior volume varying in response to fluid pressure in the chamber, a first switch, and a second switch. The chamber includes a diaphragm that is displaceable between a first configuration in response to fluid pressure above a first pressure level, a second configuration in response to fluid pressure below the first pressure level, and a third configuration in response to fluid pressure below a second pressure level. The third pressure level being lower than the second pressure level, and the second pressure level being lower than the first pressure level. The first switch is actuated by the diaphragm in the second configuration. And the second switch is actuated by the diaphragm in the third configuration.
The present invention also provides an integrated pressure management apparatus. The integrated pressure management apparatus comprises a housing defining an interior chamber, a pressure operable device, a first switch, and a second switch. The housing includes the first and second ports that communicate with the interior chamber. The pressure operable device separates the chamber into a first portion that communicates with the first port, a second portion that communicates with the second port, and a third portion that has an interior volume that varies in response to fluid pressure in the first portion. The pressure operable device is displaceable between a first configuration in response to fluid pressure in the third portion above a first pressure level, a second configuration in response to fluid pressure in the third portion below the first pressure level, and a third configuration in response to fluid pressure in the third portion below a second pressure level. The third pressure level is lower than the second pressure level, and the second pressure level is lower than the first pressure level. The first switch is actuated by the pressure operable device in the second configuration. And the second switch is actuated by the pressure operable device in the third configuration
The present invention further provides a method of detecting detecting leaks in a fuel system for an internal combustion engine that has an engine control unit. The fuel system includes a purge valve and an integrated pressure management apparatus. The integrated pressure appratus has a first switch that is activated at a first pressure level below ambient pressure, a second switch that is activated at a second pressure level below ambient, and a pressure operable device relieving excess vacuum at a third pressure level below ambient. The third pressure level is lower than the second pressure level, and the second pressure level is lower than the first pressure level. The method comprises operating the purge valve according to a first controlled duty cycle purge during operation of the internal combustion engine, indicating a gross leak, operating the purge valve according to a second controlled duty cycle purge during operation of the internal combustion engine, indicating a sealed fuel system, indicating a small leak, and indicating a large leak. The operating the purge valve according to the first controlled duty cycle purge draws a first vacuum between the first and second pressure levels. The operating the purge valve according to the second controlled duty cycle purge draws a second vacuum between the first and second pressure levels. The second vacuum is greater than the first vacuum. A gross leak is indicated if the first switch is not activated. A sealed fuel system is indicated if the first and second switches are activated. A small leak is indicated if the second switch is not activated and the first switch remains activated. And a large leak is indicated if the second switch is not activated and the first switch is intially activated and is subsequently deactivated.